The accumulation of ice on aircraft wings and other structural members in flight is a danger that is well known. As used herein, the term "structural members" is intended to refer to any aircraft surface susceptible to icing during flight, including wings, stabilizers, engine inlets, rotors, and so forth. Attempts have been made since the earliest days of flight to overcome the problem of ice accumulation.
One approach that has been used is thermal deicing. In thermal deicing, the leading edges, that is, the portions of the aircraft that meet and break the airstream impinging on the aircraft, are heated to prevent formation of ice thereon, or to loosen already accumulated ice. The loosened ice is thereby blown from the structural members by the airstream passing over the aircraft.
In one form of thermal deicing (herein referred to as electrothermal deicing), heating is accomplished by placing electrothermal pads which include heating elements over the leading edges of the aircraft, or by incorporating the heating elements into the structural members of the aircraft. Electrical energy for each heating element is derived from a generating source driven by one or more of the aircraft engines. The electrical energy is intermittently or continuously supplied to provide heat sufficient to prevent the formation of ice or to loosen accumulating ice.
Typical configurations for electrothermal deicing heating units include a wire wound, braided, or etched foil element which is arranged in a serpentine fashion. The amount of power dissipation per unit area for the deicer is regulated by varying the density of the wire within a given area by changing the spacing of the wire. This, however, is not always desirable, especially when the power density profile is changing. A decreasing power density profile requires increased wire spacing which in effect distributes the power output from the wire over a larger area. Increased wire spacing is undesirable because it results in "cold spots" between the wires do to limitations with 2-D heat transfer. Ice typically will not melt in these cold spots effectively.
Efforts to improve such variable power density electrothermal deicing systems have led to continuing developments to improve their versatility, practicality and efficiency.